Pipe protectors are tubular rubber members that surround pipe in downhole drilling operations. The rubber pipe protector contacts metal casing into which the pipe is introduced during the drilling operation. During drilling well completion fluids and drilling mud may be circulated in the annular space between the casing and the outside surface of the drill pipe. This annular space in the well also contains the pipe protector.
Pipe protectors with a slick or smooth outer surface provide maximum wear surface contacting the well casing. During the drilling operation the pipe is rapidly rotated. Directional or deviated drilling is at an angle in a non-vertical direction. The smooth surface pipe protectors are suited to high wear applications in directional drilling, but smooth pipe protectors restrict flow in tight holes.
Pipe protectors with fluted channels cut out of the outside surface provide fluid flow in tight holes. However, during rotation of the drill pipe the fluted configuration develop large vibration in tight holes especially during deviated drilling. Pipe protectors with the flutes cut in a spiral have been used. The spiral cut also produces large vibrations in deviated drilling.
The improved drill pipe protector of this invention combines the benefits of sufficient surface area for good wear characteristics and channels for fluid flow with low rotational energy requirements and vibration suppression. The tubular rubber member is sized to a pre-selected inner diameter to the approximate outside diameter of a pipe. A pattern on the outside surface of the rubber tubular member is made of raised surfaces surrounded by communicating channels. The pattern is bilaterally asymmetrical when comparing the pattern on the approximate top half of the pipe protector to the pattern on the approximate bottom half of the pipe protector. In one embodiment the pattern uses the same geometric figure such as a diamond. The diamonds are not of the same size and configuration to provide the bilateral asymmetry at the midline of the pipe protector. A combination of geometric and irregular figures can be used to create the midline asymmetry. In order to provide for fluid flow the channels comprise from about 40% to about 70% of the pattern. The raised patterned surface is from 30% to 60% of the outside surface area to minimize wear during operation. The raised surfaces may have a rounded outer contour.
The improved pipe protector can be adapted for use on pipe protectors known to those in the industry. A preferred design is a conventional split type pipe protector which has an opening the length of the tubular rubber member capable of separation at the opening to facilitate the installation on to a pipe. A closing means is provided to secure the tubular member around a pipe. Many split type pipe protectors have interlocking metal teeth covered by rubber and locked together with a key fastener inserted lengthwise through the teeth. The metal teeth are connected to a cylindrical metal insert inside the tubular rubber member. The metal insert may be smooth or corrugated metal. The split type pipe protector of the present invention has a pattern on the outside as described herein. Although the preferred embodiment of this invention is for a split type protector, the asymmetric pattern can also be used with a stretch-on type protector which is installed on the pipe by temporarily stretching or enlarging the inside diameter of the pipe protector to such a degree that the protector can be slipped over the end of the pipe.